1. Field of the Invention
Embodiments of the subject matter disclosed herein generally relate to methods and devices and, more particularly, to mechanisms and techniques for centering a driving ring in an inlet guide vane mechanism.
2. Description of Related Art
During the past years, the importance of compressors in various industries has increased. The compressors are used in engines, turbines, power generation, cryogenic applications, oil and gas, petrochemistry, etc. Thus, more research is performed for improving the efficiency of this turbomachine.
A compressor 10 includes, as shown in FIG. 1, a casing 12 that houses a shaft 14 to which an impeller 16 is attached. An inlet 18 of the compressor 10 provides the medium (usually gas) to the impeller. However, an amount of gas and a direction of the gas arriving at the impeller needs to be controlled during various functioning stages of the compressor.
An inlet guide vane (IGV) mechanism 20 may be installed in the inlet 18 for controlling the amount of gas and the direction 22 of the gas provided to the impeller 16 of the compressor 10. Such an IGV mechanism 20 is shown in FIG. 2 having a blade support disk 24 configured to hold a plurality of vanes 26. FIG. 2 shows, for simplicity, only two vanes 26. Each blade 26 is connected to a rod 28 that is configured to rotate along a longitudinal axis. A rotation of the rod 28 determines a rotation of a corresponding blade 26. Rod 28 is actuated via, for example, arms 30 and 32. Arm 30 connects to arm 32 through a bolt 34. Arm 32 is connected with a bolt 36 to a driving ring 40. The rotation of the driving ring 40 determines arms 30 and 32 to turn rod 28, and thus, blade 26. In this way, an amount of gas and a direction of the gas entering the impeller 16 is controlled by the rotation of the driving ring 40.
However, when applying a large force on the driving ring 40, for rotating it, the driving ring may also be displaced from its position, which is undesirable. Another problem that is encountered by the existing IGVs is the large thermal expansion. As the gas is forced at certain angles through the IGV, the temperature of the gas increases and the thermal expansions of the driving ring and a casing housing the driving ring may be different, which may result either in the driving ring becoming stuck to the casing or the driving ring becoming off centre. These problems of the driving ring may impact negatively the functioning of the ring and the capability to close or open the blades of the IGV, thus, impacting the functioning of the compressor.
Hartmann et al. (U.S. Patent Application Publication no. 2007/0154301, the entire content of which is incorporated herein by reference) discloses a device for supporting a ring and the device include plural levers that have a corresponding roller. The plural levers are fixed to a blade carrier and the rollers contact an adjusting ring so that the adjusting ring is supported by the rollers.
Wall (GB Patent 1 281 786, the entire content of which is incorporated herein by reference) also discloses a structure that includes rollers 159 for centering a ring 146. However, both references have a limited capability to accommodate large thermal expansions of the ring or the rollers' support or for adjusting an applied force.
Accordingly, it would be desirable to provide devices and methods that overcome the afore-described problems and drawbacks.